Computer graphic operations that are initiated by pointing devices are typically two types: command drawing operations and control operations. Drawing operations describe loci for the placement of visible marks on the image, analogous to drawing on a piece of paper by making a motion with a pen in contact with the surface. Control operations are used to initiate and guide the execution of computer functions leading to modification of the visible marks. Control operations are especially important to the performance of editing functions such as erasing, moving, or changing the visual qualities (e.g. line width) of visible marks of the image.
In a touch based input system, such control :functions are usually instituted by a menu or by a gesture command via a pointing device such as a stylus. A visible menu is either located on a specified area of a display or appears near the stylus position when desired. In order to institute a simple command from a menu, the user moves to a desired item and selects it by pressing or lifting a button on the pointing device if one were present on the device or by some other means if an ordinary pen were used. If the user does not wish to commit to a control command operation, i.e., issue any item on the menu, the user can move the pointing device off of the menu before issuing the command or move the stylus to a "cancel" selection and lift the stylus from the display. In order to institute a simple control command by gesture, the user would draw a gesture that represents some desired function and then commit to this command by lifting the input device (e.g. stylus) or a button on the device (e.g. mouse).
The commands described above however are control operations for implementing simple desired functions. Most often times user applications require complicated, i.e. complex control commands such as are shown in FIGS. 6a and 6b which entail multiple menu and sub-menus trees or highly detailed command gestures. FIG. 6a illustrates a multiple pie menu and sub-menu and FIG. 6b illustrates a multiple pull-down menu and sub-menu arrangement. In FIGS. 6a and 6b, for example, the desired function "delete" item may be located in a fourth pop-up sub-menu.
In this situation as well as many others, to save time, it would be advantageous to "hold" the complex control menu or gesture command and move within the same application program or to another program to verify that the information chosen to be deleted is actually the correct information desired. That is, it would be advantageous for a user to be able to suspend a complex menu command or command gesture before committing, perform other arbitrary commands, and then resume the suspended gesture. At present, the user must remove the complex menu command or the command gesture to perform other arbitrary commands and then return to redraw the complex gesture command or retrace the complex menu command previously desired.
One way to obtain such an advantage is to use multiple styli and concurrent commands. In such a system a user may touch a screen, draw some complex command gesture or evoke some complex menu command while maintaining contact with the screen and touch another part of the screen with a second stylus. For example, the user can begin a command gesture such as "delete file" with one stylus and hold it in place to avoid committing the command by removing the stylus. By using the second stylus to enter other commands such as "list file" the user can verify that the correct file is being deleted. Once verified the first stylus can be removed from the display surface to commit to the command. Multiple styli manipulation is neither easy nor practical.
Accordingly, it is desirable to employ a single stylus to overcome the disadvantages with multiple styli.